Sagittarius A* is nobody's fault. There was no meeting at which it was approved (but that might make for a cool scene in a sci-fi movie). In contrast, each item and action that contributes to the externality crisis has human causes: an old industry whose practices were grandfathered in; a siting decision, a regulation written to protect some sector, a banker who chose to look the other way. But the good news from this: humans can comprehend and resolve what humans cause.

We all live downwind. Literally, from a factory or a freeway shedding microplastics with every mile driven. Metaphorically, in a world shaped by the consequences of others — a warming climate, an emptying ocean, harms we inherit rather than choose. The costs are real; the accounting is incomplete.

And this is not a new observation, but it is only in the last century that economists have tried to account for it at all.